At present the molecular mechanisms involved in the formation and repair of chromosome aberrations remain to be elucidated. Even the relationship between the DNA damage and the formation of chromosome aberrations is not clearly established. This is probably due to the lack of a proper technique capable of measuring repair of chromosome damage immediately afer exposure to clastogens. Hence the primary object of this proposal is to correlate the DNA damage and repair with the formation and repair of chromosome aberrations using the recently discovered phenomenon of premature chromosome condensation (PCC). Under this project we propose to examine the following aspects: (1) The relationship between DNA repair and the formation of chromosome aberrations; (2) The relationship between DNA repair and repair of chromosome damage; (3) The effect of aging on the repair of damage to DNA and to chromosomes, and (4) The nature of the inducibility of repair enzymes. Through these experiments we hope to better understand the molecular mechanisms involved in the formation of chromosome aberrations and the relationship between damage to DNA and chromosomes, cell survival, and cellular aging. BIBLIOGRAPHIC REFERENCES: Rao, P.N., Wilson, B.A., and Puck, T.T. (1977). Premature Chromosome Condensation and Cell Cycle Analysis. J. Cell. Physiol, in press. Lau, Y.F., Hittelman, W.N., and Arrighi, F.E. (1976). Sister Chromatid Differential Staining Pattern in Prematurely Condensed Chromosomes. Experientia 32:917-918.